The truck's driver, Alan Iverson, 30, from Kelso, was driven to a local hospital with injuries from the crash. His passenger, Douglas White, 61, of North Bend, was flown to the hospital by a helicopter with serious injuries.

Officials said that Iverson was driving the dump truck downhill when he went off the road at around 10:15 a.m. and hit a tree just south of the Rice Hill exit (milepost 148).

Police said the truck flipped around the tree to face the opposite direction, coming to a stop on the side of the road.

The loaded trailer disconnected from the truck and skidded to a stop in the northbound lanes. Officials said that some cars in the southbound lanes crashed into each other while steering away from the loose trailer, expecting it to hop the cement median.

Several gallons of diesel spilled from a ruptured fuel tank and spread across the northbound lanes. The Oregon department of transportation said they closed down the slick area of roadway until crews could clean the fuel from the highway's surface.

Both men were wearing seat belts at the time of the crash. State police investigators are still looking into what caused Iverson to drive off the road.